[Rainer]

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Example: the correct model number for a 1969 Chevelle AM/FM pushbutton radio is: 91BFP1.

Using the decoding information from above, you might be confused by the "B" in the model number since "B" indicates "B-body" or in other words, a full-sized Chevy. So why is it correct for a Chevelle or mid-size "A-body" ? The answer is some of the same audio equipment was shared among different Chevrolet vehicle lines. A full-size (or B-body) Chevy such as a 1969 Impala shared the same AM/FM mono radio with such vehicles as the Camaro and the Chevelle. To keep things simple and costs down, B-body radios such as the AM/FMs were often installed in other vehicles. "B" can also be thought of as the "default" radio to be installed when a vehicle line did not have its very own line of radios. In fact, many Chevrolet vehicles "borrowed" B-body audio equipment at different times in production.

When important design changes were made to a vehicle line or the radios themselves, that vehicle's radio could no longer be "shared" with other vehicles. That's why a 1971 mid-size AM/FM mono radio has its "own" radio with a service model number of 11AFP1 because the 1971 full-size AM/FM mono radio with a service model number of 11BFP1 was no longer interchangable.[/i]

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Rick - reread the explanation that you cut and pasted from Chevelles.com and you'll see that your conclusion is not correct. As quoted above, The B radio was the default when a vehicle line did not have its very own line of radios, as in 69. In 1970 as in 71 there was a separate line of A body radios with their own number. As explained further down, That's why a 1971 mid-size AM/FM mono radio has its "own" radio with a service model number of 11AFP1 because the 1971 full-size AM/FM mono radio with a service model number of 11BFP1 was no longer interchangable.

So a unique service model number was given to a radio when the default radio was no longer interchangeable. That is exactly the case in the 1970 radios.